A new computer system is put in place at a toll booth. The system comes online at 8.00 am (with no vehicle in the queue) and vehicles arrive at a rate of λ(t)=15-0.5t (with λ(t) in veh/min and t in min). Due to a computer systems failure, cars are not serviced until 8:15 am. Between 8:15 and 8:30 they are serviced at 5 vehicles per minute. After 8:30 am they are serviced at 10 vehicles per minute. Assuming D/D/1 queueing model. 

Which option below best describes the time it takes for the queue to disappear (rounded up to the nearest one)?